Patent GB-1204918-A (GB)
Title: Electric switches
Inventor: KNIGHTS DOUGLAS SIDNEY
IPC: H01H67/24
Filed: 1967-11-16
Abstract: 1,204,918. Counters. B. & R. RELAYS Ltd. 10 Jan., 1969 [16 Nov., 1967], No. 52273/67. Heading G4D. [Also in Division H1]  An electric stepping switch comprises at least one bank of switching contact sets, a plurality of windings adapted to be operated in sequence and arranged such that successive windings in the sequence are connected to different ones of a pair of terminals energized alternately in response to a series of input pulses, each winding controlling a bi-stable contact which prepares the next winding in the sequence for operation and operates one contact set in each bank. Various arrangements with differing numbers of banks and contacts with a bank are described. In all embodiments there is provision to skip those steps for which corresponding input terminal are marked enabling hunting to be performed. A manually operated changeover switch may be included which when operated reverses the direction of the windings between the terminals and a common return causing stepping through the sequence in reverse order, or the energizing circuit for the pair of terminals may have forward and reverse inputs and include a changeover switch controlled in accordance with the input to which the pulses are applied. The arrangement shown has two banks of three contacts 1/1 to 3/2 and in response to positive input pulses applied to a terminal labelled PULSE connects to A and B firstly A1 and B1, then A2 and B2 and then A3 and B3 before reverting to A1 and B1, a positive potential applied continuously at H1, H2 or H3 causing the corresponding step to be skipped. The windings energized in sequence consists of relays RLC, RLH and RLE. A further relay RLK is arranged to be energized at the end of this sequence and via contacts K2 and K3 reverses the direction of energization of the relays RLC, RLH and RLE during the next three steps. Further relays RLI, RL2 and RL3, controlling the contacts 1/1 and 1/2, 2/1 and 2/2 and 3/1 and 3/2 respectively are connected in parallel with the associated relays RLC, RLH and RLE so as to operate simultaneously with them. Thus during a full cycle in response to six input pulses the three relays RLC, RLH and RLE are forward energized in succession in that order then reverse energized in succession in the same order while relays RLI, RL2 and RL3 are energized in succession twice in a full cycle. In another embodiment, relays equivalent to the relays RLI, RL2 and RL3 each have a diode connected in series with them so that they operate only once during a cycle and further relays (controlling further contacts like 1/1 to 3/2) each with a series diode are connected each in anti-parallel with one of the relays equivalent to the relays RL1, RL2 and RL3 so as to operate in succession during the other half cycle. In another modification the further relays are included but the series diodes are omitted the further relays each responding simultaneously with a relays equivalent to RL1, RL2 or RL3 the six relays each controlling three contacts similar to 1/1 to 3/2 and connecting three successive groups of six inputs similar to A1 to B3 to six corresponding outputs similar to A and B. The outputs may be selected three during the first half cycle and three during the second half cycle by contacts operated by the relay RLC to convert this six bank three step switch to a three bank six step switch. The driving circuit 12 shown comprises a relay RLA which responds to each pulse and a relay RLG which responds to the end of each pulse and switches a changeover contact G/3 alternately energizing the terminals 13 and 15. A relay RLF ensures that the relay RLG responds only to the end of the pulse and a relay RLB is enabled if a step is to be skipped or to revert from A3 and B3 back to A1 and B1. In a modification the relay RLF is omitted together with diodes D3 and D4 and relays RLG has the diodes D5 and D6 replaced by inductors which produce a back e.m.f. when the pulse ceases and the relay RLG responds to this back e.m.f. All contacts shown are sealed magnetic reed switches. Those which are shown as changeover switches and have the word " Red " written next to one terminal are monostable and magnetically polarized and change over to their other positions only when either winding of the associated relay is reverse energized. Those changeover contacts which have GN written next to one terminal are monostable and magnetically unpolarized and thus changeover when either winding of the associated relay is energized in either direction. Changeover contacts with BL written next to one terminal are bi-stable and change from one position to the other on forward energization of either winding and revert to their former condition when either winding is reverse energized.